Colloid stratum transfer process



United States Patent Office 3,139,449 Patented June 15, 1965 3,189,449 COLLOID STRATUM TRANSFER PROCESS Richard G. Yost, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Oct. 1, 1962, Ser. No. 227,562 4 Claims. (Cl. 96-28) This invention concerns an activator for use with the photographic process known as the colloid transfer process.

In the colloid transfer process, an image in soft adhesive organic colloid is formed photographically and a discrete stratum of the image is transferred to a receiving sheet to provide a reproduction of the subject. The process is described in the Yutzy et al. U.S. Patents 2,596,756, granted May 3, 1952, and 2,716,059, granted August 23, 1955, and embodies the exposure to a subject of substantially unhardened gelatino-silver halide emulsion layer which may contain a gelatin tanning silver halide developing agent as well as a non-tanning silver halide developing agent.

Upon activation of the exposed gelatin emulsion with the alkaline solution in the presence of the developing agent or agents, tanning development of the most exposed regions of the emulsion corresponding to the highlights of the subject proceeds, although some development of the less exposed regions also takes place to provide visual density for the transferred image as explained in more detail in U.S. Patent 2,716,059 above. Thereafter, the developed emulsion is pressed into contact with an absorbent receiving sheet such as paper to cause the less exposed regions, and thus the less developed regions, of the emulsion to adhere to the receiving sheet. Subsequently, when the emulsion and receiving sheet are separated, a stratum of the less exposed regions of the emulsion remains on the sheet and appears as a positive silver image of the original subject.

As mentioned in the above patents, the alkaline solution used for activation of the exposed emulsion layer advantageously contains a gelatin softening agent to facilitate transfer of the less exposed portions of the emulsion to the receiving sheet. Urea and certain other gelatin softening agents have been suggested for this purpose. The above patents also suggest the use of sodium carbonate'as the alkaline component of the alkaline solution used for initiating development of the exposed emulsion.

in one embodiment of the colloid transfer process, it has been proposed that the process become more automated and that the time for obtaining a copy be shorened. For this reason, it has been desirable to have an activator which would decrease the activation time formerly used and permit more rapid processing than the 15 to 20 second period normally required with known activators. In addition, certain advantages over the older activators have been sought. For instance, temperature has normally had to be regulated requiring a thermostated temperature control to keep the system at satisfactory working conditions. Therefore, it was desirable to find an activator solution which could be used between the temperatures of 60 to 90 F. without temperature regulation between these limits.

It was also desirable to increase the number of transfer matrices with a given amount of actviator solution and to have a solution that is stable for long periods in liquid form.

I have found an activator solution which can be used at room temperature containing tripotassium phosphate, potassium salicylate, and other additives such as sequestering agents, anti-foamants, and the like.

One object of this invention is to provide an improved colloid transfer activator solution having a useful temperature range of 60-90" F. Another object is to provide an improved activator solution which has a high capacity, good stability and high speed. Another object is to provide a method of preparing an activator solution which has improved characteristics. A further object is to provide a method of processing an exposed matrix for use in the colloid transfer system using an improved activator solution. Additional objects will be apparent from the following disclosure.

The above objects are attained by using an activator solution having the following components:

' Grams/liter Tripotassium phosphate 60-90 Potassium salicylate 10-40 Ethylenediamine tetraacetic acid, sodium salt 0-10 Tetraethylene glycol 0-40 Water to make 1 liter.

The 'pH of the above activator solution is approxiately 12.3 at 70 F. and the solution activates satisfactorily down to a pH of about 11.3.

The solution can be prepared from equivalent amounts of, for example, potassium hydroxide, phosphoric acid, and salicylic acid instead of the salts.

Anti-foam agents may be used, particularly in the event that the activator is to be used in a mechanical agitating device.

The following examples are intended to illustrate my invention but not to limit it in any Way.

Example 1 An activator for the colloid transfer process is prepared by dissolving grams of tripotassium phosphate in 800 ml. of water; 20 grams of potassium salicylate is added with stirring. Forty milliliters of tetraethyleneglycol and 5 grams of ethylenediamine tetraacetic acid tetrasodium salt are dissolved before bringing the volume to 1 liter.

The activator. as prepared above is used in a colloid transfer process of the type described in Yutzy et al. U.S. Patent 2,596,756. When the exposed matrix is soaked for 6 seconds and pressed in contact with a receiving sheet, a good quality image is obtained by transfer in the unexposed areas. The temperat ure of the activator is 80 F. When the temperature 'is varied over a 60-90 F. range, satisfactory transfers are obtained producing good clear images over the entire temperature range.

A tray containing 1 liter of the above activator is used to process a series of matrices. Successive copies are made until 240 sheets have been soaked and transferred, when due to loss of solution activity, the images are no longer of acceptable quality.

Example 2 An activator of the following composition is prepared:

Grams Tripotassium phosphate 80 Potassium salicylate l0 Ethylenediamine tetraacetic acid, tetrasodium salt 5 Tetraethyleneglycol 40 When this solution is used to activate a' colloid trans- .fer matrix for 6"seconds at 75 F., very good transfers are made. When the potassium salicylate is increased to 40 grams/liter, .satisfactory transfers are also obtained.

.Exaniple'4" .An'ractivator is prepared having. the following composition:. l

Grams Tripotassium phosphate: 80 Potassium salicylate T a 20 Ethylenediamin e tetraacetic acid, tetras'o dium salt-" ".Copies'are made with a 6-second activation time. However, on standingfor extended periods, an excess amount of crystallization occurs on the transfer mechanism which prevents satisfactory contactiand transfer for'subsequent Volume to 1 liter.

The'above activator works satisfactorily in the transfer processlwhen it isfreshly prepared. However, after 6 quired by the particular silver halide present in the emulsion. With daylight working emulsions limited exposure to room lights may be given during the exposure and development steps. Other emulsions may require the use of the usual safelights during the exposure and processing steps. When the proper amount of exposure has been given, gelatin tanning silver halide development occurs principally in the more highly exposed areas of the emulsion and little or no tanning development in the other areas.

When development is complete as determined by trial with the particular emulsion and conditions of'opera'tion in use, the sensitive element is pressed into contact with i an absorbent sheet such as paper by means of a squeegee blade or rollers. Immediately thereafter, the sensitive element and receiving sheet are separated leaving a stra-- use of the activator. r

r Example 5 The following composition is prepared: V V Grams Tripotassium phosphate 80' "Urea V e V 20,

Ethylenediaminetetraacetic acid, tetrasodium salt 5 months storage at 80 F., the activator fails to produce softening action so thatimages can not be transferred to the'receiving sheet. Therefore, it would be impractical.

to store such a solution for extended periodsbefore use and use within a short time wouldwbe required to obtain good results. i Exampleti. V I

.An' activator solution is prepared having the following proportions. 75 grams of .tn'sodium phosphate are dissolved in800 ml. of Water and 25 grams of sodium ,sialicylate are dissolved in the solutionj 5 grams of ethylenediamine tetraacetic acid, tetrasodium salt and 40 ml. of .tetraethylene glycol are added with water to 'bringthe solution to 1 liter; 'On soaking at'roorn temperature for 6 seconds, a transfer which had good sharpness and high quality is made to the receiving sheet. When the solution is .p'er'mittedto remain in the tray'for about two days, crystals begin to grow at the edge. and .on exposed wet j;surfaces, which interfere with normal operating proce-, dure. 7

Example 7 7 Q A substantially unhardened gelatin-silver halide emul sion (having a hardness as defined in the above patents) is prepared as described in US. Patent 2,716,059 above and containing a mixture of tanning and substantially non-tanning silver halide developing agents such as 4-.

phenylcat'e chol and'4-methoxy-a-naphthol. The emulsion is coated on a paper support and dried. The result ant sensitive element is then exposed to a two-tone subject (a line or halftone subject) if desired by reflex methods, ,and placed in the following alkaline solution of the infvention toinitiate development: I

a i i Grams. @Tripotassium phosphate 80- ;Sodium salicylate e 30 fWater to make 1 liter.

1" -When hard waters areused in makingup the above isolution, in order to prevent the formation of scale on gequipment it is advisable to add a. water softening agent,

lsuch as well known alkaline earth metal chelating agents,

; .g.,;ethyleneamiine tetraacetic acid, di-. or tetrasodium isalts, isopropanoldiarninetetraacetic acid salts, etc. About f5 grams of the salts are useful in the above formula for l jthis purpose? 7 f 7 {While development in the above .alkalinesolution is iproceeding, light should be excluded to theextent return of the less exposedand thus less hardened regions of the emulsion adheredrto the receiving sheet. The result is a positive line or halftone silver-containing image affixed to the sheet.

.The reception sheet for the process-is advantageously 7, prepared as described in the Chan et al., vU.S. Patent a 2,865,745,-issuedDecember 23.,1958, comprising a paper.

sheet on the surface of which is a mixture of an intensifying agent such as thiourea and a development suppressing agent, such as sodium formaldehyde bisulfite.

The quantity of sodium salicylate and tripotassium phosphate in the alkaline solution may be .varied' from that given in the above formula depending ,uponthe requirements of the particular emulsion used in the process. Howeventhe emulsion should have a maximum hardness of the order mentioned by theabove patents correspond. ing to a gelatin layer containing about 0.7 gram'ofdry formaldehydelper pound of gelatin freshly coated. ,For

instance, the optimum amount of tripotassium phosphate.

maybe readily determined by experimentwith difierent emulsions, development times, and temperatures. Since the tripotassium phosphate'furnishes the alkaline corn-' ponent of the solution, development is' accelerated by use.

of higher amounts and conversely slowed by lower amounts.

In a preferred embodiment of the invention the gelatin tanning and non-tanning developingagents are present in he emulsion. However, either or both developing agents may be present in the alkaline solution and the other in the emulsion. 'A very useful combination of developing agents 1 is 4-phenylc'atechol with 4-methoxy-a-naphthol. Since the latter is self-coupling, it forms a colored compound during development which contributes density to the print. halide developing agents are disclosed "by the above patents. a

The proportions used in this activatorsolution are criti- V 7 cal within the limits given above.

concentration of the tripotassium phosphate is over 160 grams/liter, transfer is difficult and excessive crystallization will occur upon evaporation. Ifthe concentration is below 60 grams/liter, the solution has a reduced useful life. 7 Y V V it will'be appreciated that the sequestering agent can 7 be some other agent than ethylenediamine tetraacetic acid tetras odiurn salt providing that it effectively sequesters calcium or other hardness cations in water used to make or dilute, the activator solution. The amount of anti- 7 foam agent would depend upon the conditions, such as pumping oragitating operations which may tend to gen erate foam; Thisamount can be judged effectively by V one skilled in'the art.

I claim:

1. A method of photographic reproduction which com-i prises developing an exposed, substantiallynon-hardened, gelatlno-silver halide. emulsion layer, said emulsion being not harder than a gelatin layer containing 0.7 gram. of formaldehyde per pound. of gelatin freshly coated, with a solution of tripotassium phosphate and potassium salicy- Other useful tanning and non-tanning silver- For instance, if the.

late in the presence of both a gelatin tanning silver halide developing agent and a substantially non-tanning silver halide developing agent to obtain a hardened gelatin and silver image in the areas of the emulsion layer corresponding to the highlights of the subject, and substantially unhardened gelatin, silver, and silver halide in the areas of the emulsion layer corresponding to the shadows of the subject, said development being such as to prevent any substantial tanning oi the emulsion layer in said areas corresponding to the shadows of the subject, pressing a sheet having an absorbent surface against said emulsion layer While said emulsion layer is moist to cause only the shadow areas of the emulsion to adhere to the sheet, and separating said sheet and emulsion layer to transfer only a stratum of said shadow areas of the emulsion layer to said sheet.

2. The process of claim 1 wherein the gelatin tanning silver halide developing agent and the substantially nontanning silver halide developing agent are present in the emulsion layer before exposure.

3. A method of photographic reproduction which comprises developing an exposed, substantially non-hardened gelatino-silver halide emulsion layer, said emulsion being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, with a solution comprising 60-90 grams/ liter of potassium phosphate, -10 grams/liter sequestering agent, -40 grams/ References Qited by the Examiner UNITED STATES PATENTS 2,156,626 5/39 Ham 96-66 2,384,592 9/45 Bean 96-66 2,596,756 5/52 Yutzy et al -28 2,625,476 1/53 Henn 96-66 2,716,059 8/55 Yutzy et a1 96-28 2,834,676 5/58 Stanley et a1. 96-66 3,043,687 7/62 Linge 96-28 OTHER REFERENCES Mees: The Theory of the ihotographic Process, 1942, p. 391.

Rose: The Condensed Chemical Dictionary, 5th ed., 1956, page 898.

NORMAN G. TORCHIN, Primary Examiner. 

1. A METHOD OF PHOTOGRAPHIC REPRODUCTION WHICH COMPRISES DEVELOPING AN EXPOSED, SUBSTANTIALLY NON-HARDENED, GELATINO-SILVER HALIDE EMULSION LAYER, SAID EMULSION BEING NOT HARDER THAN A GELATIN LAYER VONTINING 0.7 GRM OF FORMALDEHYDE PER POUND OF GELATIN FRESHLY COATED, WITH A SOLUTION OF TRIPOTASSIUM PHOSPHATE AND POTASSIUM SLICYLATE IN THE PRESENCE OF BOTH A GELATIN TANNING SILVER HALIDE DEVELOPING AGENT AND A SUBSTANTIALLY NON-TANNING SILVER HALIDE EVELOPING AGENT TO OBTAIN A HARDENED GELATIN AND SILVER IMAGE IN THE AREAS OF THE EMULSION LAYER CORRESPONDING TO THE HIGHLIGHTS OF THE SUBJECT, AND SUBSTANTIALLY UNHARDENED GELATIN, SILVER, AND SILVER HALIDE IN THE AREAS OF THE EMULSION LAYER CORRESPONDING TO THE SHADOWS OF THE SUBJECT, SAID DEVELOPMENT BEING SUCH AS TO PREVENT ANY SUBSTANTIAL TANNING OF THE EMULSION LAYER IN SAID AREAS CORRESPONDING TO THE SHADOWS OF THE SUBJECT, PRESSING A SHEET HAVING AN ABSORBENT SURFACE AGAINST SAID EMULSION LAYER WHILE SAID EMULSION LAYER IS MOIST TO CAUSE ONLY THE SHADOW AREAS OF THE EMULSION TO ADHERE TO THE SHEET, AND SEPARATING SAID SHEET AND EMULSION TO ADHERE TO THE SHEET, AND SEPARATING SAID SHEET AND EMULSION LAYER TO TRANSFER ONLY A STRATUM OF SAID SHADOW AREAS OF THE EMULSION LAYER TO SAID SHEET. 